Opisthosyllis brunnea Langerhans, 1879

Martín, Guillermo San, Hutchings, Pat & Aguado, María Teresa, 2008, Syllinae (Polychaeta, Syllidae) from Australia. Part. 2. Genera Inermosyllis, Megasyllis n. gen., Opisthosyllis, and Trypanosyllis, Zootaxa 1840, pp. 1-53 : 23-26

Opisthosyllis brunnea Langerhans, 1879

Figs 16A–I, 17A, B

Opisthosyllis brunnea Langerhans, 1879: 541 , fig. 7.- Augener 1918: 274, text-fig. 25.- Day 1967: 253, figs 12.5 c–e.- Cantone 1976: 229, figs 2, 3.- Fauvel 1953: 155, fig. 78.— Hartmann-Schröder 1979: 86; 1980: 48; 1981: 24; 1982: 58; 1991: 25, fig. 19.- San Martín 1984: 311, figs 75, 76; 1991: 230; 2003: 330, fig. 183.- Núñez et al. 1993:115, figs 2H, 3F. - Capa et al. 2001: 106. Non Opisthosyllis brunnea Imajima 1966b: 230 , text-fig. 42.- Lee & Rho 1994: 135, fig. 2.

Opisthosyllis nuchalis Verrill, 1900: 620 .- Monro 1933: 254, figs 7a–c.

Opisthosyllis australis Augener, 1913 (in part): 218, pl. 28, fig. 35.

Material examined. AUSTRALIA, WESTERN AUSTRALIA: Kimberleys, W side of Cassini Island, 13° 57'S, 125° 37'E, low tide, coll. P.A. Hutchings, 18 Jul 1988, 1 on SEM stub ( AM W31430); Inshore reef off Ned's Camp, Cape Range National Park, 21° 59'S, 113° 59'E, 1 m, intertidal, frilly alga Caulerpa sp. , coll. J.K. Lowry, 2 Jan 1984, 8 ( AM W31395); Exmouth Gulf, Bundegi Reef, N end of beach, 21° 49'S, 114° 11'E, 2 m, rocky rubble, brown alga with epiphytic growth, sticky sediments, coll. H.E. Stoddart, 4 Jan 1984, 1 ( AM W31399); Bush Bay, 30 km S of Carnarvon, 25° 10'S, 113° 39'E, 0.5 m, extensive shallow sand flats, brown algal covered cockles, coll. H.E. Stoddart, 6 Jan 1984, 1 ( AM W31400); Kalbarri, Red Bluff, 27° 42'S, 114° 09'E, 3.5 m, mixed coralline algae on rocky shore, coll. J.K. Lowry, 10 Jan 1984, 1 ( AM W31402); off S end of Long Island, Beacon Island, 28° 28' 48"S, 113° 46' 18"E, 4.5 m, dead coral substrate covered in coralline algae, coll. P.A. Hutchings, 25 May 1994, 1 ( AM W31398); SE end of Long Island, 28° 28' 48"S, 113° 46' 30"E, 8 m, dead coral substrate, covered in coralline algae, coll. P.A. Hutchings, 22 May 1994, 1 ( AM W31432); N end of Long Island, Goss Passage, 28° 28' 18"S, 113° 46' 18"E, 8 m, dead coral substrate, coralline algae, boring bivalves, coll. C. Bryce, 22 May 1994, 1 ( AM W31401); N end of Long Island, Goss Passage, 28° 27' 54"S, 113° 46' 18"E, 6 m, dead coral substrate, covered in coralline algae, coll. C. Bryce, 22 May 1994, 1 ( AM W31396). TASMAN SEA: Reef flat near "Yoshin Maru Iwaki" wreck, Elizabeth Reef, 29° 55' 48"S, 159° 01' 18"E, intertidal, from small heads of Acropora valida , Pocillopora damicornis , coll. J.K. Lowry & R.T. Springthorpe, Australian Museum Elizabeth & Middleton Reefs Expedition, 14 Dec 1987, 2( AM W31397).

Additional material. Opisthosyllis australis Shark Bay , Western Australia, 3 syntypes; (HZM V–7947), Rottnest, 1 syntype ( ZMB 53081), 1 ( ZMB 5390 ) . Opisthosyllis corallicola, Galápagos Islands , Santa Cruz, coll. & id. W. Westheide, 3 ( SMF 10747) ; Academy Bay, Santa Cruz , under stones, coll. & id. W. Westheide, 1 ( SMF 10746) ; Santa Cruz, coll. & id. W. Westheide, 4 ( SMF 10745) .

Description. Longest specimen 17 mm long, 0.85 mm wide, 92 chaetigers. Body long, with dark dorsal spots on large specimens. Prostomium oval; 4 eyes in open trapezoidal arrangement. Palps broad, elongated, longer than prostomium ( Fig. 16A). Median antenna arising from middle of prostomium, with 24 articles, slightly shorter than combined length of prostomium and palps; lateral antennae about 2/3 length of median one. Peristomium dorsally reduced, with distinct occipital flap ( Fig. 16A). Dorsal tentacular cirri longer than median antenna, with about 25 articles, about twice as long as ventral ones. Dorsal cirri all long, similar in length to body width or somewhat shorter, with basal cirrophore, whip-shaped ( Fig. 16A), most anterior longer than dorsal tentacular cirri, with about 40–50 articles; alternating long (about 30 articles) and short (about 20) from midbody to posterior end. Parapodia conical, distally bilobed ( Fig. 16A). Ventral cirri digitiform, shorter than parapodial lobes. Compound chaetae heterogomph, anterior parapodia with slender, bidentate blades, margin with short spines ( Fig. 16B); blades and shafts gradually enlarging from midbody to posterior parapodia ( Fig. 16F). Dorsal simple chaeta on posterior parapodia, slightly truncated, with minute subdistal spines ( Fig. 16H). Ventral simple chaeta on far posterior segments, unidentate, smooth ( Fig. 16I). Anterior aciculae distally blunt, 3–4 ( Fig. 16C), then 2 at midbody ( Fig. 16E), and 1 in most posterior parapodia, slender, with distally rounded tip with hollow concavity ( Fig. 16G). Pharynx usually starting on chaetigers 2–5, extending through about 7–10 segments in small and large specimens respectively; pharyngeal tooth near posterior margin of pharynx ( Fig. 16A). Proventricle through 7 segments, with about 30 muscle cell rows.

Remarks. The HZM (V–7947) syntypes of O. australis are identical to O. brunnea , while the NMW syntype has distinct dorsal papillae, thus corresponding to O. viridis (see below). The specimens reported as O. brunnea from Japan and Korea ( Lee & Rho, 1994) have a more anterior pharyngeal tooth and compound chaetae with less enlarged shafts and proportionally shorter blades with distinct spines; thus we consider that could be an undescribed species. Opisthosyllis corallicola Hartmann-Schröder, 1965 is smaller than O. brunnea , with a less well developed occipital flap, anterior compound chaetae unidentate, and more posterior shafts less enlarged; although O. corallicola was reported from the tropical Pacific, we have not found any specimen in the Australian Museum collections.

Currently, the species has a circumtropical distribution, but further studies should be addressed to assess whether it corresponds to a complex of sibling species.

Habitat. Found among dead corals, algae, sponges and other biological concretions; from intertidal to shallow depths.

Distribution. Circumtropical, including the Mediterranean; Australia (Western Australia, New South Wales, Queensland).